The US Department of Justice's (DOJ) clampdown on corruption stemming from 1MDB is a domestic affair, and should not be construed as the Americans meddling in Malaysia's business, said Amanah president Mohamad Sabu.

"We oppose US meddling in any country, just as Malaysia should not meddle in the affairs of other countries.

"The US wants to take action against those involved in bringing in illicit money to their country... (Don't accuse) the US of trying to meddle in our affairs," Mohamad said in a statement today.

He added that a royal commission of inquiry should be set up to probe this whole issue.

The DOJ yesterday filed civil suits claiming more than US$3.5 billion of 1MDB funds had been misappropriated internationally.

The US authorities are now seeking to seize more than US$1 billion in assets allegedly purchased with the siphoned monies.

Among those being targeted in the suits are Prime Minister Najib Abdul Razak's stepson Riza Aziz, and Penang-born tycoon Jho Low.

Putrajaya has said that it would cooperate with the US authorities, while at the same time insisting that Najib is not implicated in any wrongdoing by the DOJ.